The Evaluation ontology describes evaluation of seas:Propertyies. There may be:
Figure below provides an overview of the concepts in this ontology:
The seas:Property may be given a unique, constant, quality or quantity value. This is done using property seas:value.
A quality value may be any resource.
A quantity value may use external vocabularies such as QUDT (it would then be a qudt:Quantity), or OM (it would then be a om:Quantity), or be directly encoded as a literal using an appropriate datatype.
The SEAS ontologies are compatible with the QUDT ontologies. The alignment between SEAS and QUDT is expressed in an external module that imports the Evaluation ontology:
The SEAS ontologies are compatible with the OM ontologies. The alignment between SEAS and OM has not yet been expressed in an external module. Please get in contact with us if this is of interest to your project.
We are working on a custom datatype identified by cdt:ucum. The lexical value of a cdt:ucum is defined as follows :
unum ::= number ’ ’ unit number ::= noDecimalPtNumeral | decimalPtNumeral | scientificNotationNumeral unit ::= (see the Unified Code of Units of Measure specification)
noDecimalPtNumeral, decimalPtNumeral and scientificNotationNumeral are defined in the XSD 1.1 recommendation. This datatype should either be hardcoded in RDF engines, or could be specified as a Linked Datatype, making it easy for any SPARQL engine to support the comparison of quantity values.
For example, the following triples quantify the consumption of a fridge using cdt:ucum literals:
<fridge/1/consumption/frequency> seas:value "50.1 Hz"^^cdt:ucum . <fridge/1/consumption/voltage> seas:value "231 V"^^cdt:ucum . <fridge/1/consumption/tension> seas:value "2432 mA"^^cdt:ucum . <fridge/1/consumption/voltageTensionPhase> seas:value "1.68 RAD"^^cdt:ucum .
Because property values may evolve in space and time, or because they can be approximate measures or forecasts, class seas:Evaluation qualifies the link seas:value. In particular, an instance of seas:Evaluation may hold metadata about:
Let us shortly describe each of these categories.
The type of evaluation is defined by the hierarchy of seas:Evaluation sub classes. This hierarchy includes classes such as:
The W3C Spatial Data on the Web Working Group may define a best practice for describing the validity context of some entity. See Spatial Data on the Web Best Practices, W3C First Public Working Draft 19 January 2016:
Best Practice 11: How to describe properties that change over time […] When entities and their properties can change over time, or are valid only at a given time, and this needs to be captured, it is important to specify a clear relationship between property data and its versioning information.
As soon as this is the case, we recommend to use the proposed best practice. In the meantime, an evaluation validity context is described using functional sub properties of seas:hasValidityContext. The SEAS ontologies define two such properties:
Other metadata may be added to describe an evaluation instance. For example the W3C PROV Ontology enables to describe the activity that generated the evaluation, or its generation time.
Other vocabularies may be used to further describe evaluations. See the Linked Open Vocabulary cloud.
The day-ahead forecasted temperature at Aeroport de Lyon is 28.3 °C:
<air/temperature> seas:evaluation [ a seas:Forecast ; prov:wasGeneratedBy <algorithm/1/execution/234> ; prov:generatedAtTime "2016-08-12T12:00:00Z"^^xsd:dateTime ; seas:hasTemporalContext [ a time:Instant ; time:inXSDDateTime "2016-08-13T12:00:00Z"^^xsd:dateTime ] ; seas:hasSpatialContext [ a geo:Point ; geo:lat 45.7242502 ; geo:long 5.0914517 ] ; seas:evaluatedValue "28.3 °C"^^cdt:ucum ] .
The average frequency of property <fridge/1/consumption/frequency> over time interval 12:00 - 13:00, as generated by <algorithm/1/execution/12>, is 50.1054 Hz:
<fridge/1/consumption/frequency> seas:evaluation [ a seas:TimeAverageEvaluation ; prov:wasGeneratedBy <algorithm/2/execution/12> ; seas:hasTemporalContext [ a time:Interval ; time:hasBeginning [ time:inXSDDateTime "2016-09-10T12:00:00Z"^^xsd:dateTime ] ; time:hasEnd [ time:inXSDDateTime "2016-09-10T13:00:00Z"^^xsd:dateTime ] ] ; seas:evaluatedValue "50.1054 Hz"^^cdt:ucum ] .
The minimal operating value of <fridge/1/consumption/frequency> is 47.0 Hz:
<fridge/1/consumption/frequency> seas:evaluation [ a seas:MinimalOperatingValueEvaluation ; seas:evaluatedValue "47.0 Hz"^^cdt:ucum ; ] .
Evaluations qualify the link seas:value. In particular, they may hold metadata about:
Links a property to one of its evaluations.
Links an evaluation to the one and only property it evaluates.
Links an evaluation to its spatial validity context, a geo:SpatialThing.
Links an evaluation to its temporal validity context, a time:TemporalEntity.
Links some object to one of its validity contexts.
A validity context is described using functional sub properties of seas:hasValidityContext. There are two such properties defined:
Links an evaluation to the literal that qualifies some aspect of the property.
Links a property to a unique, constant, quality or quantity value for that property. A quality value may be any resource.
For example, the exact length of <car/1> is 4.27 m, and this is true in the validity context of the RDF graph.
<car/1/length> a seas:Property ; seas:value "4.27 m"^^cdt:ucum .
This property is a shortcut for an exact evaluation with all context being the most generic contexts (although this notion is not planned to be formalized).